The present invention relates to a system for improving automotive safety and specifically for a system for warning a driver when a safe distance is not maintained between vehicles.
Many automobile rear collisions are caused by a failure to maintain a safe distance between moving vehicles. To reduce the risk of these collisions a minimum separation distance should be kept between moving vehicles. A minimum separation standard recommended by the California Department of Motor Vehicles and others is a separation of the distance the vehicle travels in three seconds. This separation allows sufficient time for perception of a hazard, decision and reaction time, and mechanical braking distance. Unfortunately, many drivers either ignore this rule or are unaware of this rule. In addition, inexperienced drivers may lack the perception needed to calculate a safe separation distance. A system is needed in which a driver is automatically informed when a safe distance is not maintained between vehicles.
A number of different devices have been developed to monitor vehicle separation and enhance vehicle safety. U.S. Pat. No. 5,889,476 to Schmitz describes a device in which a collision avoidance system continuously measures a vehicle speed and a separation distance between a forward vehicle. When a minimum safe distance is not maintained between the vehicles the system automatically applies the brakes of the vehicle by switching over at least one of the engine cylinders to a compressor operation. A similar device is described in U.S. Pat. No. 3,841,427 to Di Vita. In this device a radar unit is used to determine the distance between a forward vehicle and a driver""s vehicle. A tachometer measures the speed of driver""s vehicle. A safe separation distance is calculated from the speed of the driver""s vehicle. If this separation distance is not maintained between the driver""s vehicle and the forward vehicle brakes are automatically applied.
A number of different devices have been developed which do not automatically stop the vehicle but instead simply inform the driver when a safe separation distance is not maintained. U.S. Pat. No. 5,410,304 to Hahn et al. shows a system using a radar sensor for detection of vehicle separation. The driver speed, along with weather and road conditions from sensors, is used to calculate a safe separation distance. Flashing lights warn the driver when a safe separation distance is not maintained. A similar system is shown in U.S. Pat. No. 6,014,601 to Gustafson. In this device a laser is used to determine the separation between an automobile and an object. A speedometer measures the vehicle speed from which a safe separation distance is calculated. The laser rangefinder also calculates the relative speed of the object and relative acceleration of the object with respect to the drivers vehicle. The safe separation distance is calculated from this information and road condition information. A collision time display as well as a safety danger display is provided for the vehicle""s driver. U.S. Pat. No. 6,278,360 B1 to Yanagi discloses an alternative vehicle collision warning system. In this system the speed of a drivers vehicle and a preceding or following vehicle is measured, as by transmission of signals from each of the vehicles. This device may either alert the driver or automatically apply a breaking device if the safe separation distance is not maintained.
The systems of the prior art contain a number of drawbacks. First, systems that track every event in which a safe separation distance is not maintained may prove less useful than a more selective system. At slow speeds, the danger of a collision is lower and the damage from such collision is less severe. However, if the alarm system continuously notifies the driver of every instance in which an optimal separation is not maintained there is the risk that the system would be simply ignored. In addition, there are short periods when vehicles may come into close proximity. For instance, during lane changes cars may be closer than the optimum separation distance. However, if the alarm system provides a warning at this time, the driver may become complacent or annoyed, making the alarm less useful.
In addition, the prior systems have not been able to track cars on curved roads. In separation systems that target a car in the same lane, the onboard tracking system that records the separation distance often points directly in front of or behind a vehicle. On curves, such a front pointing device could be pointing into another lane or off the road. This is problem occurs on curves, which can be the most dangerous part of a road.
It is an object of the present invention to provide an onboard automobile distance warning and alarm system that can aid a driver in maintaining a safe separation distance between vehicles. It is a further object that such a system note separation distances for vehicles in front of and vehicles behind the driver""s vehicle. It is also an object that such a system provide a warning to following vehicles that a safe separation distance is not being maintained. Such a system should be able to calculate the safe separation distance under both normal driving conditions and more hazardous driving conditions (e.g. night driving, rain, etc.).
It is an additional object to provide a system that avoids giving a warning in less dangerous conditions, such as at slower speeds or when the failure to maintain an optimal separation distance is only temporary. It is a further object to provide a system that is able to measure, using an onboard range detector, the distance of separation even when the road curves.
The above objects have been achieved with an automobile distance warning and alarm system (ADWAS). Such a system includes two rangefinders mounted on the front and rear of the driver""s vehicle respectively. The system becomes armed when the driver exceeds a selected threshold speed. The driver""s speed is used to calculate a safe separation distance, which is then compared to the distance between the driver""s vehicle and vehicles in front of or behind the driver""s vehicle (i.e. the driver""s vehicle and a proximate vehicle in the same lane). As mentioned above, a safe separation is often expressed in terms of seconds. Since distance separation equals speed times time, a separation time of three seconds at 60 mph (xcx9c90 fps) translates to a separation of 270 feet (3xc3x9790). In one embodiment, information about the weather or road conditions is input into the system to be factored into calculation of the safe separation distance. If the measured separation distance is less then a calculated safe distance, an audio and/or visual alarm alerts the driver.
In one embodiment, each rangefinder is mounted on a swivel mount that is controlled by the steering wheel. When the car turns, the rangefinder turn with the wheels, allowing continued distance calculations of cars in front of or behind the driver""s vehicle.